Gas turbine engine rotor blade having a root section with composite and metallic portions

ABSTRACT

A rotor blade for a gas turbine engine includes an airfoil section and a root section extending along a longitudinal direction between an upstream surface and a downstream surface. The root section further extends along a radial direction between an inner surface positioned at an inner end of the root section and an outer end coupled to the airfoil section. Moreover, the root section extends along a circumferential direction between a first side surface and a second side surface. Furthermore, the root section defines a longitudinal centerline extending along the longitudinal direction and positioned equidistant from the inner surface and the outer end in the radial direction. The root section includes a first portion formed from a composite material and a second portion formed from a metallic material, with the longitudinal centerline extending through the second portion of the root section.

FIELD

The present subject matter relates to gas turbine engines and, moreparticularly, to rotor blades of a gas turbine engine.

BACKGROUND

A turbofan engine typically includes a fan, a nacelle, and a core gasturbine engine positioned within the nacelle. During operation of theturbofan, the core gas turbine engine drives or otherwise rotates therotor blades of the fan relative to the nacelle. The rotation of therotor blades, in turn, generates a flow of pressurized air, which maysupport the operation of the core gas turbine and/or be used aspropulsive thrust for propelling an aircraft.

In general, a turbofan engine may have a closed rotor configuration oran open rotor configuration. More specifically, the fan is positionedwithin the nacelle in the closed rotor configuration. Conversely, in theopen rotor configuration, the fan is positioned outside of the nacelle.In this respect, the open rotor configuration generally permits the useof a larger fan than the closed rotor configuration. However, it may benecessary to position one or more metallic cables within each rotorblade of the fan when engine has an open rotor configuration. Forexample, one end of each cable is coupled to a root section of a rotorblade, while the other end of the cable is positioned within an airfoilsection of the blade.

In many instances, the rotor blades of the turbofan (e.g., the rotorblades of the fan and/or the core gas turbine engine) are formed fromcomposite materials to reduce the weight of and/or increase theoperating temperature range of the turbofan engine. However, the use ofcomposite materials in turbofan engine rotor blades presents variouschallenges. For example, it is difficult to securely couple a metalliccable to the root section of a composite fan rotor blade.

Accordingly, an improved rotor blade of a gas turbine engine would bewelcomed in the technology.

BRIEF DESCRIPTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In one aspect, the present subject matter is directed to a rotor bladefor a gas turbine engine. The rotor blade includes an airfoil sectionand a root section extending along a longitudinal direction between anupstream surface of the root section and a downstream surface of theroot section. The root section further extends along a radial directionbetween an inner surface positioned at an inner end of the root sectionand an outer end coupled to the airfoil section. Moreover, the rootsection extends along a circumferential direction between a first sidesurface and a second side surface. Furthermore, the root section definesa longitudinal centerline extending along the longitudinal direction andpositioned equidistant from the inner surface and the outer end in theradial direction. The root section includes a first portion formed froma composite material and a second portion formed from a metallicmaterial, with the longitudinal centerline extending through the secondportion of the root section.

In another aspect, the present subject matter is directed to a gasturbine engine. The gas turbine engine includes a fan, a compressorsection, a turbine section, and a rotor blade positioned within one ofthe fan, the compressor section, or the turbine section. The rotorblade, in turn, includes an airfoil section and a root section extendingalong a longitudinal direction between an upstream surface of the rootsection and a downstream surface of the root section. The root sectionfurther extends along a radial direction between an inner surfacepositioned at an inner end of the root section and an outer end coupledto the airfoil section. Moreover, the root section extends along acircumferential direction between a first side surface and a second sidesurface. Furthermore, the root section defines a longitudinal centerlineextending along the longitudinal direction and positioned equidistantfrom the inner surface and the outer end in the radial direction. Theroot section includes a first portion formed from a composite materialand a second portion formed from a metallic material, with thelongitudinal centerline extending through the second portion of the rootsection.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 is a schematic cross-sectional view of one embodiment of a gasturbine engine;

FIG. 2 is a side view of one embodiment of a rotor blade of a gasturbine engine;

FIG. 3 is a partial perspective view of one embodiment of a root sectionof a rotor blade of a gas turbine engine;

FIG. 4 is a cross-sectional view of the root section taken generallyabout line 4-4 in FIG. 4, particularly illustrating a longitudinalcenterline of the root section extending through various composite andmetallic portions of the root section;

FIG. 5 is a cross-sectional view of the root section taken generallyabout line 5-5 in FIG. 4, particularly illustrating a metallic portionof the root section partially forming various surfaces of the rootsection;

FIG. 6 is a partial cross-sectional view of another embodiment of a rootsection of a rotor blade of a gas turbine engine, particularlyillustrating the composite portions of the root section forming thesurfaces of the root section;

FIG. 7 is a partial cross-sectional view of a further embodiment of aroot section of a rotor blade of a gas turbine engine, particularlyillustrating a metallic portion of the root section extending outwardalong a radial direction beyond a bottom end of an airfoil section ofthe rotor blade; and

FIG. 8 is a partial cross-sectional view of yet another embodiment of aroot section of a rotor blade of a gas turbine engine, particularlyillustrating a metallic portion of the root section having a differentcross-sectional shape than a composite portion of the rotor blade.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present invention.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

As used herein, the terms “first”, “second”, and “third” may be usedinterchangeably to distinguish one component from another and are notintended to signify location or importance of the individual components.

Furthermore, the terms “upstream” and “downstream” refer to the relativedirection with respect to fluid flow in a fluid pathway. For example,“upstream” refers to the direction from which the fluid flows, and“downstream” refers to the direction to which the fluid flows.

Additionally, the terms “low,” “high,” or their respective comparativedegrees (e.g., lower, higher, where applicable) each refer to relativespeeds within an engine, unless otherwise specified. For example, a“low-pressure turbine” operates at a pressure generally lower than a“high-pressure turbine.” Alternatively, unless otherwise specified, theaforementioned terms may be understood in their superlative degree. Forexample, a “low-pressure turbine” may refer to the lowest maximumpressure turbine within a turbine section, and a “high-pressure turbine”may refer to the highest maximum pressure turbine within the turbinesection.

In general, the present subject matter is directed to a rotor blade fora gas turbine engine. As will be described below, the disclosed rotorblade may be incorporated into a fan, a compressor, or a turbine of thegas turbine engine. More specifically, the rotor blade includes anairfoil section and a root section. The root section, in turn, extendsalong a longitudinal direction between an upstream surface and adownstream surface. Furthermore, the root section extends along a radialdirection between an inner surface positioned at an inner end and anouter end coupled to the airfoil section. In this respect, the rootsection defines a longitudinal centerline extending along thelongitudinal direction and positioned equidistant from the inner surfaceand the outer end in the radial direction.

The root section of the rotor blade is formed from a combination ofcomposite and metallic materials. Specifically, in several embodiments,the root section includes one or more portions formed from a compositematerial, such as ceramic matrix composite (CMC) material. Moreover, insuch embodiments, the root section includes one or more portions formedfrom a metallic material, such as a titanium-, aluminum-, and/ornickel-based alloy. Moreover, the longitudinal centerline of the rootsection extends through the metallic portion(s). In some embodiments,the metallic portion(s) form portions of the exterior surfaces of theroot section. However, in other embodiments, the composite portion(s)form the external surfaces of the root section (i.e., the metallicportion(s) may be encased within the composite portion(s)).

Using a rotor blade root section having a composite portion(s) and ametallic portion(s), with the longitudinal centerline of the rootsection extending through the metallic portion(s), provides varioustechnical advantages. For example, one or more metallic cables may bepositioned within the rotor blade. One end of each metallic cable, inturn, is coupled to (e.g., embedded within) a metallic portion of theroot section, thereby providing a more secure connection than couplingthe cable(s) to an entirely composite root section. Additionally, theinclusion of the composite portion(s) within the rotor blade (as opposedto an entirely metallic root section) reduces the weight of andincreases the operating temperature range of the rotor blade.

Referring now to the drawings, FIG. 1 is a schematic cross-sectionalview of one embodiment of a gas turbine engine 10. In the illustratedembodiment, the engine 10 is configured as an open rotor or unductedturbofan engine. However, in alternative embodiments, the engine 10 maybe configured as a closed rotor or ducted turbofan engine, a turbojetengine, a turboprop engine, a turboshaft gas turbine engine, or anyother suitable type of gas turbine engine.

In general, the engine 10 includes a fan 12 and a core engine 14extending along an axial centerline 16. More specifically, the fan 12may include a fan rotor 18 and a plurality of fan rotor blades 20 (oneis shown) coupled to the fan rotor 18. In this respect, the fan rotorblades 20 are spaced apart from each along the circumference of the fanrotor 18 and extend outward from the rotor 18. Moreover, the core engine14 may be positioned downstream from the fan 12 along the axialcenterline 16. As shown, the core engine 14 is rotatably coupled to thefan rotor 18 via a low-pressure (LP) shaft 22, thereby permitting thecore engine 14 to rotate the fan 12.

In several embodiments, the engine 10 also includes a nacelle or outercasing 24 surrounding various components of the core engine 14. Morespecifically, the nacelle 24 generally surrounds or encases, in serialflow order, a compressor section 26, a combustion section 28, a turbinesection 30, and an exhaust section 32. For example, in some embodiments,the compressor section 26 may include a low-pressure (LP) compressor 34and a high-pressure (HP) compressor 36 positioned downstream from the LPcompressor 34 along the axial centerline 12. Each compressor 34, 36 may,in turn, include one or more rows of stator vanes 38 interdigitated withone or more rows of compressor rotor blades 40. Moreover, in someembodiments, the turbine section 30 includes a high-pressure (HP)turbine 42 and a low-pressure (LP) turbine 44 positioned downstream fromthe HP turbine 42 along the axial centerline 12. Each turbine 42, 44may, in turn, include one or more rows of stator vanes 46 interdigitatedwith one or more rows of turbine rotor blades 48.

Additionally, the engine 10 includes the low-pressure (LP) shaft 22 anda high pressure (HP) shaft 50 positioned concentrically around the LPshaft 22. In such embodiments, the HP shaft 50 rotatably coupled therotor blades 48 of the HP turbine 42 and the rotor blades 40 of the HPcompressor 36 such that rotation of the HP turbine rotor blades 48rotatably drives HP compressor rotor blades 40. As shown, the LP shaft22 is directly coupled to the rotor blades 48 of the LP turbine 44 andthe rotor blades 40 of the LP compressor 34. Furthermore, the LP shaft22 is coupled to the fan 12 via a gearbox 52. In this respect, therotation of the LP turbine rotor blades 48 rotatably drives the LPcompressor rotor blades 40 and the fan blades 20.

In several embodiments, the engine 10 may generate thrust to propel anaircraft. More specifically, during operation of the engine 10, the fan12 pressurizes incoming air (indicated by arrow 54). In this respect, afirst portion (indicated by arrow 56) of the pressurized air 54 flowsaround the nacelle 24 (i.e., external to the nacelle 24) toward the rearof the engine 10. Conversely, a second portion (indicated by arrow 58)of the air 54 is directed into the compressor section 26 of the coreengine 14. The second portion 58 of the air 54 first flows through theLP compressor 34 in which the rotor blades 40 therein progressivelycompress the second portion 58 of the air 54. Next, the second portion58 of the air 54 flows through the HP compressor 36 in which the rotorblades 40 therein continue progressively compressing the second portion58 of the air 54. The compressed second portion 58 of the air 54 issubsequently delivered to the combustion section 28. In the combustionsection 28, the second portion 58 of the air 54 mixes with fuel andburns to generate high-temperature and high-pressure combustion gases60. Thereafter, the combustion gases 60 flow through the HP turbine 42in which the HP turbine rotor blades 48 extract a first portion ofkinetic and/or thermal energy therefrom. This energy extraction rotatesthe HP shaft 50, thereby driving the HP compressor 36. The combustiongases 60 then flow through the LP turbine 44 in which the LP turbinerotor blades 48 extract a second portion of kinetic and/or thermalenergy therefrom. This energy extraction rotates the LP shaft 22,thereby driving the LP compressor 40 and the fan 12 via the gearbox 52.The combustion gases 60 then exit the core engine 14 through the exhaustsection 32.

The configuration of the gas turbine engine 10 described above and shownin FIG. 1 is provided only to place the present subject matter in anexemplary field of use. Thus, the present subject matter may be readilyadaptable to any manner of gas turbine engine configuration, includingother types of aviation-based gas turbine engines, marine-based gasturbine engines, and/or land-based/industrial gas turbine engines.

FIG. 2 is a side view of one embodiment of a rotor blade 100, which maybe incorporated into the engine 10 in place of any of the fan rotorblades 20, the compressor rotor blades 40, and/or the turbine rotorblades 48. As shown, the rotor blade 100 defines a longitudinaldirection L, a radial direction R, and a circumferential direction C. Ingeneral, the longitudinal direction L extends parallel to the axialcenterline 16 of the engine 10, the radial direction R extends generallyorthogonal to the axial centerline 16, and the circumferential directionC extends generally concentrically around the axial centerline 16.

In several embodiments, the rotor blade 100 includes an airfoil section102 and a root section 104. More specifically, in such embodiments, theairfoil section 102 extend outward from the root section 102 to a tip106 along the radial direction R. Furthermore, the airfoil 102 includesa pressure-side surface 108 and an opposing suction-side surface (notshown). In this respect, the pressure side surface 108 and the suctionside surface are joined together or interconnected at a leading edge 110of the airfoil 102 and a trailing edge surface 112 of the airfoil 102.Additionally, as will be described below, the root section 104 securesthe rotor blade 100 to a rotor disk (not shown) coupled the LP shaft 22(FIG. 1) or HP shaft 50 (FIG. 1). However, in alternative embodiments,the rotor blade 100 may have any other suitable configuration. Forexample, in one embodiment, the rotor blade 100 may include a platformpositioned between the airfoil section 102 and the root section 104along the radial direction R.

FIGS. 3-5 are various views of one embodiment of a root section 104 ofthe rotor blade 100. Specifically, FIG. 3 is a partial perspective viewof the root section 104. Moreover, FIG. 4 is a cross-sectional view ofthe root section 104 taken generally about line 4-4 in FIG. 4. Inaddition, FIG. 5 is a cross-sectional view of the root section 104 takengenerally about line 5-5 in FIG. 4.

As shown in FIGS. 3-5, the root section 104 extends along thelongitudinal, radial and circumferential directions L, R, C. Morespecifically, the root section 104 extends along the longitudinaldirection L between an upstream surface 114 of the root section 104 anda downstream surface 116 of the root section 104. Furthermore, the rootsection 104 extends along the radial direction R between an inner end118 of the root section 104 and an outer end 120 of the root section104, with an inner surface 122 of the root section 104 positioned at theinner end 118. The outer end 120 of the root section 104, in turn,couples to an inner end 124 of the airfoil section 102. Additionally,the root section 104 extends along a circumferential direction C betweena first side surface 126 and a second side surface 128. Moreover, asbest illustrated in FIG. 4, the root section 104 defines a longitudinalcenterline 130 extending along the longitudinal direction L andpositioned equidistant from the inner surface 122 of the root section104 and the outer end 120 of the root section 104 in the radialdirection R.

In several embodiments, the root section 104 may have a dovetailconfiguration. More specifically, as shown in FIGS. 3 and 5, in suchembodiments, the side surfaces 126, 128 extend outward (i.e., away fromthe longitudinal centerline 130) in the circumferential direction C asthe root section 104 extends inward along the radial direction R fromits outer end 120 to a position 132 located between the inner and outerends 118, 120 along the radial direction R. Furthermore, the sidesurfaces 126, 128 extend inward (i.e., toward from the longitudinalcenterline 130) in the circumferential direction C as the root section104 extends inward along the radial direction R from the position 132 toits inner end 118. Thus, the side surfaces 126, 128 may define V-likeshapes that provide the root section 104 with a dovetail configuration.However, in alternative embodiments, the root section 104 may have anyother suitable configuration, such as a collet or a fir treeconfiguration.

Additionally, as shown in FIGS. 3-5, one or more metallic cables 134 maybe coupled to otherwise partially positioned within the root section104. Specifically, when the gas turbine engine (e.g., the engine 10) hasan open rotor configuration, it may be necessary to position one or moremetallic cables 134 with the rotor blades 100 of the associated fansection (e.g., the fan section 12). As such, in several embodiments, themetallic cable(s) 134 may be partially positioned within the airfoilsection 102 and partially positioned within the root section 104. Forexample, each metallic cable 134 may extend from a first end 136positioned within the root section 104 and a second end (not shown)positioned within the airfoil section 102. As will be described below,the first end 136 of each metallic cable 134 may be coupled to a portionof the root section 104. Moreover, the metallic cable(s) 134 may beformed of any suitable metallic material, such as a titanium-,aluminum-, or nickel-based alloy.

Furthermore, the root section 104 includes one or more portions 138formed from a composite material and one or more portions 140 formedfrom a metallic material. Specifically, in several embodiments, thecomposite portions 138 may be positioned between the metallic portions140. For example, as shown in FIGS. 3 and 4, in the illustratedembodiment, the root section 104 includes first second, and thirdcomposite portions 138A, 138B, 138C and first and second metallicportions 140A, 140B. In this respect, the first metallic portion 140A ispositioned between the first composite portion 138A and the secondcomposite portion 138B along the longitudinal direction L. Similarly,the second metallic portion 140B is positioned between the secondcomposite portion 138B and the third composite portion 138C along thelongitudinal direction L. In this respect, the first composite portion138A forms the upstream surface 114 of the root section 104, while thethird composite portion 138C forms the downstream surface 116 of theroot section 104. However, in alternative embodiments, the root section104 may include any other suitable number of composite and/or metallicportions 138, 140. Moreover, the composite and/or metallic portions 138,140 may be positioned or arranged within the root section 104 in anyother suitable manner.

Moreover, the composite portions 138 of the root section 104 may beformed from any suitable composite material. For example, the compositematerial may be selected from the group consisting of, but not limitedto, a ceramic matrix composite (CMC), a polymer matrix composite (PMC),a metal matrix composite (MMC), or a combination thereof. Suitableexamples of matrix material for a CMC matrix is ceramic powder,including but not limited to, silicon carbide, aluminum-oxide, siliconoxide, and combinations thereof. Suitable examples of matrix materialfor a PMC include, but are not limited to, epoxy-based matrices,polyester-based matrices, and combinations thereof. Suitable examples ofa MMC matrix material include, but are not limited to powder metals suchas, but not limited to, aluminum or titanium capable of being meltedinto a continuous molten liquid metal which can encapsulate fiberspresent in the assembly, before being cooled into a solid ingot withincased fibers. The resulting MMC is a metal article with increasedstiffness, and the metal portion (matrix) is the primary load caringelement.

Furthermore, the metallic portions 140 of the root section 104 may beformed from any suitable metallic material. In several embodiments, themetallic portions may be formed from the same metallic material as themetallic cable to facilitate a secure connection therebetween. Forexample, the metallic portions may be formed a titanium-, aluminum-, ornickel-based alloy.

Forming the root section 104 from one or more composite portions 138 andone or more metallic portions 140 provides various technical advantages.More specifically, as best illustrated in FIG. 4, the longitudinalcenterline 130 of the root section 104 extends through each metallicportion 140. That is, a region of each metallic portion 140 ispositioned at the radial center of the root section 104. Moreover, inseveral embodiments, the first end 136 of each metallic cable 134 iscoupled to one of the metallic portions 140. For example, as shown inFIGS. 4 and 5, in the illustrated embodiment, the first end 136 of oneof the metallic cables 134 is embedded or otherwise encased within thefirst metallic portion 140A, while the first end 136 of the othermetallic cable 134 is embedded or otherwise encased within the secondmetallic portion 140B. In this respect, coupling the first end(s) 136 ofthe metallic cable(s) 134 to the metallic portion(s) of the root section104 provides a more secure connection than coupling the cable(s) to anentirely composite root section. That is, a metal-to-metal connection isstronger than a metal-to-composite connection. Furthermore, positioningthe metallic portion(s) at the radial center of the root section furtherincreases the strength of the cable/root coupling. Additionally, theinclusion of the composite portion(s) within the root section 104 (asopposed to an entirely metallic root section) reduces the weight of andincreases the operating temperature range of the rotor blade 100.

The metallic portion(s) 140 of the root section 104 may be exposed orencased by the composite portions 138. Specifically, in someembodiments, the metallic portion(s) 140 may be exposed such that themetallic portion(s) 140 form regions of one or more surfaces of the rootsection 104. For example, in the embodiment of the root section 104shown in FIGS. 3-5, the metallic portion(s) 140 form regions of theinner surface 122, the first side surface 126, and the second sidesurface 128. In other embodiments, the metallic portion(s) 140 may beencased within or otherwise enclosed by the composite portion(s) 138. Insuch embodiments, the composite portion(s) 138 form the entirety of thesurfaces of the root section 104. For example, in the embodiment shownin FIG. 6, the metallic portion(s) 140 is enclosed by the compositeportion(s) 138 such that the composite portion(s) 138 defines theupstream surface 114, the downstream surface 116, the inner surface 122,the first side surface 126, and the second side surface 128.

As shown in FIGS. 4 and 5, in several embodiments, the metallicportions(s) 140 may be positioned inward along the radial direction Rfrom the inner end 124 of the airfoil 102. In such embodiments, themetallic portion(s) 140 may not extend outward along the radialdirection R past the outer end 120 of the root section 104. However, asshown in FIG. 7, in other embodiments, the metallic portion(s) 140 mayextend outward along the radial direction R past the inner end 124 ofthe airfoil 102. In such embodiments, a region(s) of the metallicportion(s) 140 may be positioned outward from the inner end 124 of theairfoil section 102 in the radial direction R.

In addition, the composite and metallic portion(s) 138, 140 of the rootsection 104 may have any suitable cross-sectional shape. Specifically,in several embodiments, the metallic portion(s) 140 may have the samecross-sectional shape (i.e., in a plane defined by the radial andcircumferential directions R, C) as the composite portion(s) 138 and/orthe overall root section 104. For example, in the embodiments shown inFIGS. 5 and 6, the metallic portion(s) 140 has the same dovetailcross-sectional shape as the composite portion(s) 138 and the overallroot section 104. In other embodiments, the metallic portion(s) 140 mayhave a different cross-sectional shape (i.e., in the plane defined bythe radial and circumferential directions R, C) than the compositeportion(s) 138 and/or overall root section 104. For example, in theembodiment shown in FIG. 8, the metallic portion(s) 140 has arectangular cross-sectional shape, while the composite portion(s) 138and the overall root section 104 have dovetail cross-sectional shapes.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

Further aspects of the invention are provided by the subject matter ofthe following clauses:

A rotor blade for a gas turbine engine, the rotor blade comprising: anairfoil section; and a root section extending along a longitudinaldirection between an upstream surface of the root section and adownstream surface of the root section, the root section furtherextending along a radial direction between an inner surface positionedat an inner end of the root section and an outer end coupled to theairfoil section, the root section further extending along acircumferential direction between a first side surface and a second sidesurface, the root section defining a longitudinal centerline extendingalong the longitudinal direction and positioned equidistant from theinner surface and the outer end in the radial direction, the rootsection including a first portion formed from a composite material and asecond portion formed from a metallic material, wherein the longitudinalcenterline extends through the second portion of the root section.

The rotor blade of one or more of these clauses, further comprising: ametallic cable partially positioned within the airfoil section andpartially positioned within the root section, the metallic cableincluding an end coupled to the second portion of the root section.

The rotor blade of one or more of these clauses, wherein the end of themetallic cable is embedded within the second portion of the rootsection.

The rotor blade of one or more of these clauses, wherein the firstportion of the root section forms the upstream surface, the downstreamsurface, the inner surface, the first side surface, and the second sidesurface.

The rotor blade of one or more of these clauses, wherein the secondportion of the root section forms a portion of at least one of the innersurface, the first side surface, or the second side surface.

The rotor blade of one or more of these clauses, wherein the secondportion of the root section forms a portion of the inner surface, thefirst side surface, and the second side surface.

The rotor blade of one or more of these clauses, wherein the rootsection further includes a third portion formed from the metallicmaterial, the third portion of the root section spaced apart from thesecond portion of the root section in the longitudinal direction.

The rotor blade of one or more of these clauses, wherein the firstportion of the root section is positioned between the second portion ofthe root section and the third portion of the root section along thelongitudinal direction.

The rotor blade of one or more of these clauses, further comprising: afirst metallic cable coupled to the second portion of the root section;and a second metallic cable coupled to the third portion of the rootsection.

The rotor blade of one or more of these clauses, wherein the rootsection defines a dovetail cross-sectional shape.

The rotor blade of one or more of these clauses, wherein the firstportion of the root section and the second portion of the root sectiondefine the same cross-sectional shape.

The rotor blade of one or more of these clauses, wherein the firstportion of the root section and the second portion of the root sectiondefine different cross-sectional shapes.

The rotor blade of one or more of these clauses, wherein the secondportion of the root section extends outward along the radial directionbeyond an inner end of the airfoil section.

The rotor blade of one or more of these clauses, wherein the compositematerial comprises a ceramic matrix composite or a polymeric matriccomposite.

The rotor blade of one or more of these clauses, wherein the metallicmaterial comprises at least one of titanium, aluminum, or nickel.

A gas turbine engine, comprising: a fan; a compressor section; a turbinesection; and a rotor blade positioned within one of the fan, thecompressor section, or the turbine section, the rotor blade comprising:an airfoil section; a root section extending along a longitudinaldirection between an upstream surface of the root section and adownstream surface of the root section, the root section furtherextending along a radial direction between an inner surface positionedat an inner end of the root section and an outer end coupled to theairfoil section, the root section further extending along acircumferential direction between a first side surface and a second sidesurface, the root section defining a longitudinal centerline extendingalong the longitudinal direction and positioned equidistant from theinner surface and the outer end in the radial direction, the rootsection including a first portion formed from a composite material and asecond portion formed from a metallic material, wherein the longitudinalcenterline extends through the second portion of the root section.

The gas turbine engine of one or more of these clauses, furthercomprising: a metallic cable partially positioned within the airfoilsection and partially positioned within the root section, the metalliccable including an end coupled to the second portion of the rootsection.

The gas turbine engine of one or more of these clauses, wherein the endof the metallic cable is embedded within the second portion of the rootsection.

The gas turbine engine of one or more of these clauses, wherein thefirst portion of the root section forms the upstream surface, thedownstream surface, the inner surface, the first side surface, and thesecond side surface.

The gas turbine engine of one or more of these clauses, wherein thesecond portion of the root section forms a portion of at least one ofthe inner surface, the first side surface, or the second side surface.

What is claimed is:
 1. A rotor blade for a gas turbine engine, the rotorblade comprising: an airfoil section; a root section extending along alongitudinal direction between an upstream surface of the root sectionand a downstream surface of the root section, the root section furtherextending along a radial direction between an inner surface positionedat an inner end of the root section and an outer end coupled to theairfoil section, the root section further extending along acircumferential direction between a first side surface and a second sidesurface, the root section defining a longitudinal centerline extendingalong the longitudinal direction and positioned equidistant from theinner surface and the outer end in the radial direction, the rootsection including a first portion formed from a composite material and asecond portion formed from a metallic material; and a metallic cablepartially positioned within the airfoil section and partially positionedwithin the root section, the metallic cable including an end coupled tothe second portion of the root section, wherein the longitudinalcenterline extends through the second portion of the root section. 2.The rotor blade of claim 1, wherein the end of the metallic cable isembedded within the second portion of the root section.
 3. The rotorblade of claim 1, wherein the first portion of the root section formsthe upstream surface, the downstream surface, the inner surface, thefirst side surface, and the second side surface.
 4. The rotor blade ofclaim 1, wherein the second portion of the root section forms a portionof at least one of the inner surface, the first side surface, or thesecond side surface.
 5. The rotor blade of claim 4, wherein the secondportion of the root section forms a portion of the inner surface, thefirst side surface, and the second side surface.
 6. The rotor blade ofclaim 1, wherein the root section further includes a third portionformed from the metallic material, the third portion of the root sectionspaced apart from the second portion of the root section in thelongitudinal direction.
 7. The rotor blade of claim 6, wherein the firstportion of the root section is positioned between the second portion ofthe root section and the third portion of the root section along thelongitudinal direction.
 8. The rotor blade of claim 6, wherein themetallic cable corresponds to a first metallic cable, the rotor bladefurther comprising: a second metallic cable coupled to the third portionof the root section.
 9. The rotor blade of claim 1, wherein the rootsection defines a dovetail cross-sectional shape.
 10. The rotor blade ofclaim 1, wherein the first portion of the root section and the secondportion of the root section define the same cross-sectional shape. 11.The rotor blade of claim 1, wherein the first portion of the rootsection and the second portion of the root section define differentcross-sectional shapes.
 12. The rotor blade of claim 1, wherein thesecond portion of the root section extends outward along the radialdirection beyond an inner end of the airfoil section.
 13. The rotorblade of claim 1, wherein the composite material comprises a ceramicmatrix composite or a polymeric matrix composite.
 14. The rotor blade ofclaim 1, wherein the metallic material comprises at least one oftitanium, aluminum, or nickel.
 15. A gas turbine engine, comprising: afan; a compressor section; a turbine section; and a rotor bladepositioned within one of the fan, the compressor section, or the turbinesection, the rotor blade comprising: an airfoil section; a root sectionextending along a longitudinal direction between an upstream surface ofthe root section and a downstream surface of the root section, the rootsection further extending along a radial direction between an innersurface positioned at an inner end of the root section and an outer endcoupled to the airfoil section, the root section further extending alonga circumferential direction between a first side surface and a secondside surface, the root section defining a longitudinal centerlineextending along the longitudinal direction and positioned equidistantfrom the inner surface and the outer end in the radial direction, theroot section including a first portion formed from a composite materialand a second portion formed from a metallic material; and a metalliccable partially positioned within the airfoil section and partiallypositioned within the root section, the metallic cable including an endcoupled to the second portion of the root section, wherein thelongitudinal centerline extends through the second portion of the rootsection.
 16. The gas turbine engine of claim 15, wherein the end of themetallic cable is embedded within the second portion of the rootsection.
 17. The gas turbine engine of claim 15, wherein the firstportion of the root section forms the upstream surface, the downstreamsurface, the inner surface, the first side surface, and the second sidesurface.
 18. The gas turbine engine of claim 15, wherein the secondportion of the root section forms a portion of at least one of the innersurface, the first side surface, or the second side surface.
 19. A rotorblade for a gas turbine engine, the rotor blade comprising: an airfoilsection; and a root section extending along a longitudinal directionbetween an upstream surface of the root section and a downstream surfaceof the root section, the root section further extending along a radialdirection between an inner surface positioned at an inner end of theroot section and an outer end coupled to the airfoil section, the rootsection further extending along a circumferential direction between afirst side surface and a second side surface, the root section defininga longitudinal centerline extending along the longitudinal direction andpositioned equidistant from the inner surface and the outer end in theradial direction, the root section including a first portion formed froma composite material and a second portion formed from a metallicmaterial, the second portion of the root section forming a portion of atleast one of the inner surface, the first side surface, or the secondside surface, wherein the longitudinal centerline extends through thesecond portion of the root section.
 20. The rotor blade of claim 19,wherein the second portion of the root section forms a portion of theinner surface, the first side surface, and the second side surface.